Validation of the firefighter WFI treadmill protocol for predicting VO2 max

Area of Science:

• Exercise Physiology
• Occupational Health

Background:

• The Wellness-Fitness Initiative submaximal treadmill exercise test (WFI-TM) is recommended for assessing firefighter aerobic capacity (VO2 max).
• Submaximal tests can lead to inaccurate VO2 max predictions and flawed fitness conclusions.

Purpose of the Study:

• To evaluate the agreement between predicted VO2 max from the WFI-TM and direct VO2 max measurement.
• To identify potential biases and errors in WFI-TM VO2 max predictions.

Main Methods:

• Fifty-nine male firefighters performed the WFI-TM to volitional fatigue.
• VO2 max was estimated using the WFI-TM equation and directly measured via exhaled gas analysis.
• Paired t-tests, Pearson correlation, and Bland-Altman analysis assessed agreement and bias.

Main Results:

• WFI-TM predicted VO2 max (44.6 ml/kg/min) showed significant agreement with measured VO2 max (43.6 ml/kg/min) (P < 0.01).
• A mean bias of 0.9 ml/kg/min overestimated VO2 max, with a wide 95% prediction interval (±13.1).
• Prediction errors exceeded 15% for 36% of subjects, and 7% had errors over 30%.

Conclusions:

• The WFI-TM predicts VO2 max with an average error of 11%, potentially misclassifying firefighter fitness.
• Aerobic capacity tends to be overestimated in less fit individuals and underestimated in fitter individuals.
• This bias can affect fitness-for-duty decisions, especially around the 42 ml/kg/min threshold.